Thickness dependence of JcS in YBCO, TL-2212 and HG-1212 thick films

Epitaxial growth of thick (typically a few microns) high-T-c superconducting (HTS) films on metal substrates is desired for coated conductor applications in order to carry high electrical current of several thousands amperes per centimeter width. Serious degradation of the critical current (J(c)) at large film thickness in YBa2CU3O7 (YBCO) films has raised a question on the mechanism related. To understand such mechanisms, we have investigated the thickness dependence of J(c)s in several different types of HTS thick films including YBCO, Tl2Ba2CaCu2O7+delta (Tl-2212), and HgBa2CaCu2O6+delta (Hg-1212). By comparing materials with different anisotropy that may affect the thickness dependence of J(c)s, and microstructures that are resulted from different processing, we intend to pinpoint the mechanisms that are responsible for the degradation of the J(c) in HTS thick films.